Electrically controlled screwcutting machine



4Y Sheets-.Sheet v1 Feb. 19, 1935. R, HERRMANN Er AL ELECTRICALLY CONTROLLED SCRW CUTTING MACHINE Filed April 23, 19:54

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ELECTRICALLY CONTROLLED SCREW CUTTING MACHINE yFiled April 23, 1934 4 Sheets-Sheet 2 25 63 62 66 El 68 a F ig fm l-l [llllll-llllll l`IIIIIL xlllllll mlm l "mu [f5 Ullmann" """Efuum /NvervTOlS Feb. 19, 1935. R, HERRMANN Er AL 1,991,927 Y ELECTRICALLY CONTROLLED SCREW CUTTING MACHINE Filed Avpil 23; 1954 4 Sheets-Sheet 3 g. Her/"77787271,

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ELECTRICALLY CONTROLLED SCREW CUTTING MACHINE Filed April 25, 1934 4 Sheets-Sheet 4 j 1 U Eo'= 75 'f6 w 'f1 lfa'fo 6 if Flaw ng 11 Lw lf3 leo a9 In lf3 uo 39 Illlllllllllllllllllllllllllllll Herrmann E. ffy/efr' warm Nve/V TOKS Patented Feb. 19, 1.935. l A

ELECTRICALLY CONTROLLED SCREW- CUTTING MACHINE Richard Herrmann and Ernst-Herrmann, Stuttgart, Germany Application April 23, 1934, Serial No. 122,035 In Germany May 8, 1 933 'z claims. (ci. 11i-136) This invention relates to avscrew cutting matracted. When the reversing switch is released chine, the axially displaceable spindle of which for the purpose of initiating a, fresh working is rotated in both directions alternately by an' stroke, the detent liberates the switch, which now, electric motor, preferably a three-phase motor, under the action of the spring-controlled snap 5 the reversal of the direction of rotation being device, is thrown over into the forward position. 5 il'ected in a manner known in itself by'reversing The driving motor, and with it the spindle and e polarity of the driving motor. 'I'his reversal the feed gear that displaces them axially, now of the direction of rotation is effected in known run forwards, until the spindle has reached its machines of this kind by means of a magnetically lower limiting position, which is determined by controlled change-over relay, which is reversed. an adjustable reversing stop, which moves in de- 10 by means of suitable control contacts, which are pendence upon the longitudinal displacement changed over from time to time to the opposite of the spindle'. This reversing stop now brings direction of rotation by the axially reciprocating the reversing switch into its return position.- The spindle in its end positions. This known arrangedriving motor and the spindle now run backwards, i5 ment is .very complicated owing to the employuntil the motor is again reversed inte the eriaini 15 ment of a special change-over relay controlled by position, in which the control switch is again rea greatly branched auxiliary circuit, and requires versed by asecond reversing stop to the idle posiexpert supervision. tion, out of which it drops into the iforward posi- It has now been found that the reversing contion by release 0! the frementiened IOekins tacts, such as are employed in magnetically actumeansated change-over relays, also admit of being en- Now a screw-cutting machine of the kind mentirely mechanically actuated directly' by a suittioned, in which theV spindle is axially displaced able switching mechanism, which is reversed by by an amount approximately equal to the pitch -the axially displaceable working spindle in the of the screw at every revolution, must still fulfill end positions, vand that the expensive and very the condition that the direction of rotation is u complicated magnetically actuated change-over reversed after a definite time even if the screw relay thereby becomes unnecessary, as a result tap should not cut, whether it be that it is acciof which a material simplification and cheapendentally mounted upon an undrilled piece of. ing of the machine is attainable, with enhanced work, or the cut has become too blunt. In order reliability of operation. in this case to prevent injury to the machine 30 q 'I'he length of travel of the working spindle, there is interposed in ya known-manner in the which is axially displaced by a special feed gear, path of the power of the feed drive a buffer which may be constructed as a leading screw or, spring which limits the feeding power to the as shown later in the constructional example, permissible amount. In order to enable a reveras a worm and rack drive, through a distance sal to be effected at the right time even when 35 equal to about the pitch of the thread to be cut this buffer spring responds, according to the inat each revolution, is under these circumstances vention another auxiliary stop is provided, which determined, in a manner known in itself, by is connected with the part of the feed gear premeans of movable reversing stops. ceding the buffer spring. This is so adjusted 40 Now it has been found specially advantageous in relation to the main stop that when the work 4 in Screw-Cutting machines 0f this type to stop is proceeding normally it does not come into the spindle in the intervals between the individ- Muon,l 1f, however, the spindle is held up, so' ual working periods, partly beeeuse the 101181- that it cannot move axially, the auxiliary stop tudmal movement of the spindle can thereby be overtakes the main stop towards the conclusion 45 ls'gteadni exigglm' tlrfg bfscasgr; of the stroke, and reverses the direction of rotafacilitated and rendered safe. Thel reversing 33u after the spmdle hais executed a predeterned number of revolutions. switch constructed asa quick-break switch is 1 -f f th therefore locked in the new machine at the end one constructiona'l exam!) e o e new Screw' of each working stroke by a locking device, while cutting machine diagrammatiauy ilustra'd 50 it is reversed by the spindle from its forward m the accompanymg drawmgs' m Whlh position to its return position immediately after Figure 1 ShOWS a longitudinal SeCtiOn thlOllS the quick-break switch has passed beyond its mid the machine; position. The switch cannot therefore lsnap over Figure 2 Shows a Section 'siens the line into the forward position before the detent is re- A-B-C-D-E;

Figure 3 is a cross section through the locking means of the reversing switch;

Figure 4 is a sectional elevation through the switch contacts;

Figure 5 is a cross section through the buffer spring casing, the switching means being shown therein in the locked position;

Figure 6 shows the switching means in the forward position;

Figure 7 shows the switching means at the moment of snapping over;

Figure 8 shows the switch in the return position;

Figure 9 shows the reversing switch in cross section;

Figure 10 shows the switch contacts in th forward position; and

Figure 11 in the backward position;

Figure 12 is a circuit diagram of the machine for three-phase motor drive;

Figure 13 is a circuit diagram of the machine for continuous-current motor drive, and

Figure 14 shows a modification. A

The spindle 1 of the machine is journalled in bearing bushes 2 and 3 in a. bearing sleeve 4, which is guided in a bore 5 in a casing 6. A pin screw 7, which engages in a groove 8 in the bearing sleeve, limits its longitudinal movement and prevents it from rotating. The spindle 1 carries at its lower end a clamping chuck .9 for a screw tap 10. Upon the upper end of the spindle l is mounted a toothed wheel 11, which meshes with a toothed wheel 12 mounted upon theshaft 14 of a driving motor 13.

'Ihe feed gearing V of the spindle 1 is driven by a pinion 15, which is likewise mounted upon the motor shaft 14. lThis drives a worm shaft 16 by means of a toothed wheel v17, this worm shaft being journalled in bearings 18 and 19 in the casing 6. The worm 20 meshes with a worm wheel 21, which is rotatably mounted upon a transverse shaft 22, and by the friction disc 23, against which it is pressed by the brake spring 24, and thereby carried round with a limited peripheral power. vUpon one end ofthe transverse shaft 22 is mounted a change wheel 25, which drives a pinion shaft 27 by means of a second change wheel 26. Upon the pinion shaft 27 is mounted loose a pinion 28, which meshes with teeth 29 on the bearing sleeve 4. The pinion shaft 27 and the pinion 28 are rotatably coupled by ring springs 30 and 31, which lie in an annular groove 32 in a stop disc 33, which is connected fast with the pinion 28 by a hollowI shaft 34. The ring springs 30 and 31 are located between tappets 35 and 36, one of which is secured to the stop disc 33 and the other to a tappet disc 37, which is fixedly mounted upon the end of the pinion shaft 27. The pinion 28 can therefore only rotate against the action of the buer spring 30, so that the peripheral force of the pinion 28 in feeding is limited to a definite amount..

The shorter and stronger buffer spring 31 is only intended for taking up incidental rotations during the return.

In a cavity 38 in the lower part of the casing 6 is lodged a reversing switch U. Upon its switch shaft 39 is mounted internally a contact arm 40, with which contact springs 41 and 42 are connected by insulating pieces 43. The contact springs 41 and 42 carry at their free ends contacts 44 and 45, which are located between fixed pairs of contacts 46, 47 and 48, 49, which are embedded in an insulating piece 50 connected with the casing 6. The contact springs-41 and 42 are connected by movable conductors 51 withthe connection terminals 52.

The switch shaft 39 is controlled for a quick break by a snap pin 53 (Figs. 2, 5 and 6), which is guided in a transverse bore 54 in a head piece 55 on the switch shaft 39. The snap pin 53 is pressed outwards by a spring 56, and is limited in its movement and prevented from rotating by a pin 57. The snap pin 53 has at its end a knife edge 58, which is opposite to a knife edge 59 on a swing lever 60, which can execute, about a bearing extension 61, a swinging movement which is limited by a notch 62 and a stop pin 63 mounted fast on the casing 6, as shown in Figs. 2, 5 and 7.

Now the swing lever 60 is moved alternately from one extreme position intothe other by stops 64 and 65, which are so clamped on to the dovetailed rim 66 of the stop disc 33 as to be adjustable in a peripheral direction. They strike at the end of each forward and backward movement against a tappet pin 67 mounted on the swing lever 60. Upon the neckof the tappet disc 37 is also clamped an auxiliary stop 68, which can likewise come into engagement with the pin 67.

In order to enable the switch shaft 39 to be locked in the mid position, there is arranged parallel to it a locking bolt 69, on the flattened head end 70 of which there strikes a projection 71 on the head piece 55. A compression spring 72 brings the projection into the locked position. It can be retracted by a releasing lever 73 for the purpose of liberating the switch shaft 39.

The casing 6 is mounted by its rear bore 74 upon a column 75 on'a table frame 76, and can be firmly clamped at the required height by means of screws 77.

In the position of rest, which is shown in Figure 1, the supply contacts 44 and 45 are located free between the forward contacts 46 and 47 and the return contacts 48 and 49, and the motor 13 is therefore without current. Under these circumstances the switch control assumes the position shown in Figure 5, in which the switch shaft 39 is held fast in the mid position by the locking bolt 69. The snapping pin 53, which is subject to the stress of the compression spring 56, has thrown over the swing lever 60 for right-handed rotation, until it bears with its slot or notch 62 against the stop pin 63, while the switch shaft 39 tends to rotate to the right.

If the locking bolt 69 is drawn back by depressing the releasing lever `73, its extension 70 sets free the extension 71 on the head piece 55, and with it the switch shaft 39. 'I'he snap pin 53 now springs forward-and swings the switch shaft 39 to the right, until the movable supply contacts 44 and 45 stand upon the forward contacts 46 and 47 respectively. The driving motor 13 now drives the spindle 1 in the forward direction. Under these circumstances the bearing sleeve 4 is displaced forward by the pair of wheels l5 and 17, the pair of change wheels 25 and 26, the pinion 28, and the rack teeth 29 by -an amount which is preferably somewhat greater than the pitch of the screw to be cut, and which admits' of being regulated by changing the change wheels 25 and 26. Any difference between the pitch of the threads and the actual advance is equalized by the buffer springs 30 and 31.

The spindle 1 now runs in a forward direction until the reversing stop 65 takes the cutting lever 60 with it by means of the tappet pin 67. The latter rotates therefore in an anti-clockwise direction until it has reached the position shown in Figure 7. 4Until then the snap pin 53 has been pressed inwards and the switch shaft 39, owing to its spring stress, has been kept in right-handed rotation, that is to say, in the forward position. Now as soon as the edge 59 of the swing lever 60 has passed the co-acting edge 58 on the snap pin 53, the latter springs forward and throws the swing lever 60 and the switch shaft 39 over into the return position shown in Figure 8. In this position the snap pin 53 tends to rotate the swing lever 60 and the switch shaft 39 in an anti-clockwise direction, until the former again bears with its notch 62 on the stop pin 63 and the movable supply contacts 44 and 45 come into contact with the return contacts 48 and 49. 'I'he driving motor is thereby reversed, the screw tap 10 screws out of the work, and the spindle l is retracted by forward position again, but is locked in the mid position by the locking surfaces 70 and 71. The driving motor 13 is therefore again fully switched oif and de-energized, and remains stationary after slowing down and stopping. Since it may occur that the driving motor continues to run when the bearing sleeve 4 is already locked in its end position by the stop pin, the feeding worm wheel 21 is rotatably connected by the friction clutch 23 and 24 with the worm shaft 22, for the purpose of obviating over-loading of the feed gear.

If the screw tap is accidentally mounted upon an undrilled portion, or does not cut out, so that the spindle cannot advance, the buffer spring 30 becomes compressed to an extent corresponding to the depth of cut. and the feed pinion 28 located behind it remains stationary. Now since the reversing stop 65. is rigidly connected with the latter by the stop disc 33, this stop cannot reach the tappet pin 67, and therefore can-y not reverse the machine. In order to obviate this disadvantage another auxiliary stop 68 is provided. which is connected with the pinion shaft 27. and thereby reverses the motor even if the buffer spring 30 responds to a greater feed path. The two stops 65 and 68 therefore work in such a way that the stop 65 reverses when a definite depth of thread is reached, whereas the auxiliary stop 68 reverses, independently of the position of the spindle 1, after the latter has executed a definite number of revolutions. 'I'he auxiliary stop 68 is therefore preferably so ad- Justed that when the working operation is proceeding normally, it just does not reach the tap-- pet pin 67 when the main stop 65 reverses the motor.

For the driving of such a machine a threephase motor with a short-circuited rotor is best suited. A circuit diagram of the connections vof such a motor is shown in Figure 12. Of the three connection terminals of the motor D. one is directly connected with one of the three leads. The other two are connected crosswise with the contacts 46 and 47 or 48 and 49 respectively, which are connected alternately with the other two leads alternately by the movable lever contacts 44 and 45 with the two leads.

The unlocking of the reversing switch, which is effected in the constructional example hereinbefore described by means of the manual releasing lever 73, may alternatively be effected in some other way. It has been found particularly advantageous to effect this unlocking by the pull of a magnet, as illustrated in Figure 14. By means of this device it is possible to effect the release from any convenient position, without any effort. merely by closing a contact. It is also possible by this means to set a number of such machines in operation simultaneously. In the form of construction illustrated in Fig. 14, there is secured to the rear end of the locking bolt 69 an armature plate 80, which is a short distance from a magnet core 81. Upon the latter is mounted a magnet coil 82, which is surrounded by a cap 83, which forms the external closure of the magnetic flux. When the magnet coil 82 is excited, the magnet l core 81 attracts the armature plate 80 as a result of which the locking bolt 69 connected therewith is retracted, and the switch shaft 39 is set free.

What we claim is:- 1. A screw-cutting machine comprising a spindle, a reversible electric motor for rotating the spindle in both directions alternately, a reversing switch for changing the direction of rotation of the motor, a feeding device for displacing the spindle longitudinally, a snap-action mechanism adapted to operate the reversing switch, a reversing stop carried by the feeding device and controlling the snap-action mechanism and a releasable lock adapted to hold the reversing switch open after the snap-action mechanism has been changed over from the backward running position into the forward running position.

2. A screw-cutting machine as claimed in claim 1, wherein the releasable lock comprises a longitudinally movable bar adapted to engage releasably with the reversing switch.

3. A- screw-cutting machine comprising a spindie, a reversible electric motor for rotating the spindle in both directions alternately, a reversing switch for changing the direction of rotation of the motor, a feeding device for displacing the spindle longitudinally, a snap-action mechanism adapted to operate the reversing switch, a reversing stop carried by the feeding device and adapted to throw the snap-action mechanism over from a backward running position into a forward running position a releasable lock adapted to hold the reversing switch open after the snap-action mechanism has been changed over from thebackward running position into the forward running position, a second reversing stop carried by the feeding device and adapted to throw the snap-action mechanism over from the forward running position into the backward running position when the spindle has reached a definite depth, a buffer spring interposed between the feeding device and the spindle, and an auxiliary reversing stop adapted to throw the snap-action mechanism over from the forward running position into the backward running position after the spindle has executed a definite number of revolutions.

4. A screw-cutting machine as claimed in claim 1, further comprising an electro-magnet for releasing the lock.

5. A screw-cutting machine as claimedvin claim Y 3, the said buffer spring being an annular coil spring.

6. A screw-cutting machine as claimed in claim 3, further comprising a spring casing for the buffer spring, this spring casing also constituting a carrier for the reversing stops.

7. A screw-cutting machine as claimed in claim 3, further comprising a spring casing for the buffer spring, and an over-running clutch, this spring casing also constituting a carrier for the reversing stops, and its lateral edge constituting a brake disc for the overrunning clutch.

RICHARD HERRMANN. ERNST HERRMANN. 

